With increasing public awareness regarding persons with disabilities, many local and regional laws, regulations, and ordinances have been passed that require modifications to existing structures and consideration of the disabled when undertaking new construction. Perhaps the most significant new legislation has been the enactment of the Americans with Disabilities Act (ADA). This Act sets forth numerous requirements regarding access to and use of facilities by the disabled.
One of the more widely recognized disabilities is impaired vision. While previously the incorporation of tactile indicia and detectible warnings was discretionary, under the ADA suitable tactile indicia and detectible warnings must be provided in many situations. Moreover, the types of acceptable detectible warnings are now regulated.
Specifically, the ADA now requires detectible warnings on the walking surface of curb ramps or on a walking surface prior to it crossing or adjoining a vehicular way not otherwise separated by curbs, railings, or other such elements. Similarly, if there are no curbs, railings, or the like between a walking surface and perhaps a reflecting pool, detectible warnings must be used.
Detectible warnings have been defined as "a standardized integral surface feature built in or applied to walking surfaces or other elements to warn individuals with visual impairments of hazards on a circulation path." The technical specifications of the ADA require that detectible warnings on walking surfaces have a specific truncated dome pattern. Although the standardization requirement has been reserved, this unique pattern is intended to provide a consistent and uniform surface that is distinctive from other materials and, therefore, recognizable as a warning to pedestrians that they are approaching a potentially dangerous area. The detectible warnings must contrast visually with adjoining surfaces, and material used to provide contrast must be an integral part of the walking surface. Though not required, a 70% contrast ratio is recommended. Detectible warnings used on interior surfaces shall differ from adjoining walking surfaces in resiliency or sound-on-cane contact.
When discussing detectible warnings for pedestrians, three traditional techniques of achieving such warnings have been used: surface forming, etching, and deposition. In surface forming, a desired pattern is created in the surface during its formation stage. For example, when a concrete walk is being formed, the detectible warning pattern is created therein usually by stamping the surface or by applying a prefabricated surface treatment. Etching, if done during the formation of the surface, provides a low cost method for treating a traveled surface to have the required detectible warning. However, if etching is desired on an existing surface, a material removal process must usually be used which often incorporates the use of abrasives or the like. With both of these means, however, there is little ability to incorporate visual contrast or other required or desirable aspects identified in the ADA.
Deposition techniques are usually carried out after the surface formation process has been completed. Thus, such techniques are suitable for both new and old work. A significant problem associated with many other deposition techniques is that the resulting detectible warnings may be abrupt so as to engender the tripping of a person using that surface. In addition, many surfaces having detectible warnings are slippery and/or lack contrast when compared to the base surface. Moreover, it is desirable to have detectible warnings that are uniform in appearance--a quality that some deposition techniques fail to provide.